1. Field of the Invention
This invention relates to an electric motor drive device for a camera automatically set in a winding completed state in response to detection of film rewinding completion when the film used comes to an end while still incompletely wound within the camera.
2. Description of the Prior Art
After completely photographing all film frames, further winding brings the film to an end leaving the film in a state of being pulled by a motor. To prevent the film from breaking and the motor from overheating, in the conventional camera electric drive devices, the power supply to the motor is stopped and a light emitting diode is turned on to indicate the end of the film. In some of the conventional electric motor drive devices, the power supply to the motor is stopped part way through the winding process by a switch interlocked with a film counter and then the end of the film is displayed.
To rewind the film, a sprocket is released by opening a power source switch (or a counter is released where a counter is provided) for rewinding. In this instance, with the power source cut off, the power supply to the motor is stopped and a circuit for displaying the end of the film is reset to erase the display of the end of the film. After completion of film rewinding, when the power source switch is again turned on, the power supply to the motor is resumed to set the camera into a winding completed state from its uncompleted winding state. In this instance, the winding completed state is attained for a predetermined length of time after commencement of the power supply to the motor. Therefore, the film end display is not lighted.
In another method, when a film end display is made with the power supply to the motor stopped, film rewinding is carried out with the film end display left on; then, after completion of rewinding, the camera is set into a winding completed state by means of a camera winding lever; and the power supply to the motor is stopped and a circuit for the film end display is reset to permit the next photographic operation.
Each of the conventional methods has thus necessitated the step of setting the camera into a winding completed state either by turning the power supply on and off or by operating a winding lever. It has been impossible to perform the next photographic operation without carrying out these processes. Furthermore, in cases where the mechanical phase of the camera body and the mechanical phase within the electric motor drive device are interrelated, if the camera body and the motor drive device are separated from each other in an uncompleted winding state and then are coupled with another camera body or electric drive device which is at a different phase, this out-of-phase combination hinders normal functions from being performed until the different phases coincide with each other.
Electric motor drive cameras provided with electric motor winding and rewinding facilities include a type in which, after completion of photography for a predetermined number of frames, a winding process is performed. The winding process is performed in association with the switch of a film counter and is stopped halfway. Then, in carrying out the motor rewinding operation, the camera is set into a winding completed state in association with the release of the counter and a sprocket. However, this arrangement is nothing more than setting the camera into a winding completed state. Since this setting is effected before commencement of the electric motor rewinding operation, if a shutter release is effected during the process of the rewinding operation, the shutter would expose the film being rewound to light.
It is an object of the present invention to provide an electric motor drive device for a camera which is capable of obviating the above-stated shortcomings of the prior art by automatically setting the camera into a winding completed state upon completion of film rewinding to solve the discrepancy in phase arising between the camera body and the electric motor drive device when they are separated from each other.
It is another object of the invention to provide an electric motor drive device for a camera in which a film detection signal terminal disposed between the camera body and the electric motor drive device is also usable for other signals.